Hello,
[ 2.375503] ======================================================
[ 2.375504] [ INFO: possible circular locking dependency detected ]
[ 2.375505] 4.7.0-next-20160727-dbg-00004-g32e4851-dirty #770 Not tainted
[ 2.375506] -------------------------------------------------------
[ 2.375507] kworker/u16:3/119 is trying to acquire lock:
[ 2.375526] (&dev->mode_config.mutex){+.+.+.}, at: [<ffffffffa0281ebc>] drm_modeset_lock_all+0x4f/0xb7 [drm]
[ 2.375527]
but task is already holding lock:
[ 2.375532] ((fb_notifier_list).rwsem){++++.+}, at: [<ffffffff81062f9e>] __blocking_notifier_call_chain+0x31/0x64
[ 2.375533]
which lock already depends on the new lock.
[ 2.375533]
the existing dependency chain (in reverse order) is:
[ 2.375535]
-> #1 ((fb_notifier_list).rwsem){++++.+}:
[ 2.375539] [<ffffffff81087465>] lock_acquire+0x130/0x1c4
[ 2.375541] [<ffffffff813ba23e>] down_write+0x3b/0x6a
[ 2.375543] [<ffffffff81062d05>] blocking_notifier_chain_register+0x33/0x53
[ 2.375546] [<ffffffff8121d0df>] fb_register_client+0x18/0x1a
[ 2.375549] [<ffffffff8121ca85>] backlight_device_register+0x145/0x1c5
[ 2.375593] [<ffffffffa05a8e2b>] intel_backlight_device_register+0xdc/0x137 [i915]
[ 2.375634] [<ffffffffa057efd3>] intel_connector_register+0xe/0x10 [i915]
[ 2.375675] [<ffffffffa0596396>] intel_dp_connector_register+0x1b/0x70 [i915]
[ 2.375689] [<ffffffffa027381d>] drm_connector_register+0x5c/0x80 [drm]
[ 2.375702] [<ffffffffa0275870>] drm_modeset_register_all+0x156/0x19e [drm]
[ 2.375713] [<ffffffffa026fb20>] drm_dev_register+0x7c/0xc7 [drm]
[ 2.375747] [<ffffffffa05028e0>] i915_driver_load+0xf3e/0x1040 [i915]
[ 2.375782] [<ffffffffa050b91c>] i915_pci_probe+0x3f/0x41 [i915]
[ 2.375785] [<ffffffff8120416f>] pci_device_probe+0x83/0xeb
[ 2.375789] [<ffffffff81299d51>] driver_probe_device+0x118/0x261
[ 2.375790] [<ffffffff81299f0d>] __driver_attach+0x73/0x95
[ 2.375792] [<ffffffff8129804a>] bus_for_each_dev+0x6f/0x87
[ 2.375794] [<ffffffff8129975a>] driver_attach+0x1e/0x20
[ 2.375796] [<ffffffff81298f3a>] bus_add_driver+0xf6/0x1e6
[ 2.375797] [<ffffffff8129ab5d>] driver_register+0x88/0xbf
[ 2.375800] [<ffffffff812031e9>] __pci_register_driver+0x5d/0x60
[ 2.375830] [<ffffffffa0629062>] i915_init+0x62/0x66 [i915]
[ 2.375833] [<ffffffff8100043e>] do_one_initcall+0x90/0x118
[ 2.375835] [<ffffffff810f9910>] do_init_module+0x5f/0x1f1
[ 2.375839] [<ffffffff810b97f6>] load_module+0x1b00/0x2053
[ 2.375841] [<ffffffff810b9e48>] SyS_init_module+0xff/0x125
[ 2.375844] [<ffffffff813bc225>] entry_SYSCALL_64_fastpath+0x18/0xa8
[ 2.375846]
-> #0 (&dev->mode_config.mutex){+.+.+.}:
[ 2.375849] [<ffffffff810869d9>] __lock_acquire+0xf09/0x15a1
[ 2.375851] [<ffffffff81087465>] lock_acquire+0x130/0x1c4
[ 2.375853] [<ffffffff813b823e>] mutex_lock_nested+0x70/0x32d
[ 2.375865] [<ffffffffa0281ebc>] drm_modeset_lock_all+0x4f/0xb7 [drm]
[ 2.375872] [<ffffffffa04b5b8f>] drm_fb_helper_restore_fbdev_mode_unlocked+0x2e/0x6d [drm_kms_helper]
[ 2.375878] [<ffffffffa04b5c0d>] drm_fb_helper_set_par+0x3f/0x4b [drm_kms_helper]
[ 2.375917] [<ffffffffa058d22a>] intel_fbdev_set_par+0x17/0x56 [i915]
[ 2.375919] [<ffffffff8121997d>] fbcon_init+0x35f/0x464
[ 2.375922] [<ffffffff8126eca3>] visual_init+0xd6/0x12a
[ 2.375924] [<ffffffff8127004e>] do_bind_con_driver+0x1a0/0x2a6
[ 2.375926] [<ffffffff812702bb>] do_take_over_console+0x167/0x191
[ 2.375929] [<ffffffff812178c6>] do_fbcon_takeover+0x60/0x9a
[ 2.375931] [<ffffffff8121a5e8>] fbcon_event_notify+0x434/0x763
[ 2.375934] [<ffffffff81062cae>] notifier_call_chain+0x3e/0x62
[ 2.375936] [<ffffffff81062fb9>] __blocking_notifier_call_chain+0x4c/0x64
[ 2.375938] [<ffffffff81062fe5>] blocking_notifier_call_chain+0x14/0x16
[ 2.375940] [<ffffffff8121d116>] fb_notifier_call_chain+0x1b/0x1d
[ 2.375941] [<ffffffff8121de8e>] register_framebuffer+0x293/0x2cf
[ 2.375948] [<ffffffffa04b5ec0>] drm_fb_helper_initial_config+0x2a7/0x32d [drm_kms_helper]
[ 2.375986] [<ffffffffa058dc5e>] intel_fbdev_initial_config+0x18/0x28 [i915]
[ 2.375988] [<ffffffff81063f2d>] async_run_entry_fn+0x37/0xcd
[ 2.375991] [<ffffffff8105b77e>] process_one_work+0x2b1/0x59e
[ 2.375993] [<ffffffff8105c768>] worker_thread+0x24f/0x38a
[ 2.375995] [<ffffffff81061b7c>] kthread+0xf8/0x100
[ 2.375997] [<ffffffff813bc43f>] ret_from_fork+0x1f/0x40
[ 2.375998]
other info that might help us debug this:
[ 2.375998] Possible unsafe locking scenario:
[ 2.375999] CPU0 CPU1
[ 2.375999] ---- ----
[ 2.376000] lock((fb_notifier_list).rwsem);
[ 2.376002] lock(&dev->mode_config.mutex);
[ 2.376003] lock((fb_notifier_list).rwsem);
[ 2.376004] lock(&dev->mode_config.mutex);
[ 2.376004]
*** DEADLOCK ***
[ 2.376005] 6 locks held by kworker/u16:3/119:
[ 2.376009] #0: ("events_unbound"){.+.+.+}, at: [<ffffffff8105b663>] process_one_work+0x196/0x59e
[ 2.376012] #1: ((&entry->work)){+.+.+.}, at: [<ffffffff8105b663>] process_one_work+0x196/0x59e
[ 2.376015] #2: (registration_lock){+.+.+.}, at: [<ffffffff8121dc22>] register_framebuffer+0x27/0x2cf
[ 2.376018] #3: (console_lock){+.+.+.}, at: [<ffffffff8121de6c>] register_framebuffer+0x271/0x2cf
[ 2.376021] #4: (&fb_info->lock){+.+.+.}, at: [<ffffffff8121d8f2>] lock_fb_info+0x1d/0x3c
[ 2.376025] #5: ((fb_notifier_list).rwsem){++++.+}, at: [<ffffffff81062f9e>] __blocking_notifier_call_chain+0x31/0x64
[ 2.376025]
stack backtrace:
[ 2.376027] CPU: 2 PID: 119 Comm: kworker/u16:3 Not tainted 4.7.0-next-20160727-dbg-00004-g32e4851-dirty #770
[ 2.376030] Workqueue: events_unbound async_run_entry_fn
[ 2.376033] 0000000000000000 ffff88041a9fb7f0 ffffffff811d980b ffffffff81f1f400
[ 2.376035] ffffffff81f226a0 ffff88041a9fb830 ffffffff81083b78 ffff88041a9ea980
[ 2.376037] ffff88041a9eb178 0000000000000006 ffff88041a9eb1a0 ffff88041a9ea980
[ 2.376038] Call Trace:
[ 2.376041] [<ffffffff811d980b>] dump_stack+0x68/0x92
[ 2.376044] [<ffffffff81083b78>] print_circular_bug+0x286/0x294
[ 2.376046] [<ffffffff810869d9>] __lock_acquire+0xf09/0x15a1
[ 2.376049] [<ffffffff81087465>] lock_acquire+0x130/0x1c4
[ 2.376051] [<ffffffff81087465>] ? lock_acquire+0x130/0x1c4
[ 2.376063] [<ffffffffa0281ebc>] ? drm_modeset_lock_all+0x4f/0xb7 [drm]
[ 2.376075] [<ffffffffa0281ebc>] ? drm_modeset_lock_all+0x4f/0xb7 [drm]
[ 2.376077] [<ffffffff813b823e>] mutex_lock_nested+0x70/0x32d
[ 2.376088] [<ffffffffa0281ebc>] ? drm_modeset_lock_all+0x4f/0xb7 [drm]
[ 2.376100] [<ffffffffa0281e92>] ? drm_modeset_lock_all+0x25/0xb7 [drm]
[ 2.376102] [<ffffffff810981c2>] ? rcu_read_lock_sched_held+0x61/0x69
[ 2.376114] [<ffffffffa0281ebc>] drm_modeset_lock_all+0x4f/0xb7 [drm]
[ 2.376125] [<ffffffffa0281ebc>] ? drm_modeset_lock_all+0x4f/0xb7 [drm]
[ 2.376131] [<ffffffffa04b5b8f>] drm_fb_helper_restore_fbdev_mode_unlocked+0x2e/0x6d [drm_kms_helper]
[ 2.376138] [<ffffffffa04b5c0d>] drm_fb_helper_set_par+0x3f/0x4b [drm_kms_helper]
[ 2.376175] [<ffffffffa058d22a>] intel_fbdev_set_par+0x17/0x56 [i915]
[ 2.376178] [<ffffffff8121997d>] fbcon_init+0x35f/0x464
[ 2.376180] [<ffffffff8126eca3>] visual_init+0xd6/0x12a
[ 2.376182] [<ffffffff8127004e>] do_bind_con_driver+0x1a0/0x2a6
[ 2.376184] [<ffffffff812702bb>] do_take_over_console+0x167/0x191
[ 2.376186] [<ffffffff812178c6>] do_fbcon_takeover+0x60/0x9a
[ 2.376188] [<ffffffff8121a5e8>] fbcon_event_notify+0x434/0x763
[ 2.376191] [<ffffffff81062cae>] notifier_call_chain+0x3e/0x62
[ 2.376193] [<ffffffff81062fb9>] __blocking_notifier_call_chain+0x4c/0x64
[ 2.376196] [<ffffffff81062fe5>] blocking_notifier_call_chain+0x14/0x16
[ 2.376197] [<ffffffff8121d116>] fb_notifier_call_chain+0x1b/0x1d
[ 2.376199] [<ffffffff8121de8e>] register_framebuffer+0x293/0x2cf
[ 2.376206] [<ffffffffa04b5ec0>] drm_fb_helper_initial_config+0x2a7/0x32d [drm_kms_helper]
[ 2.376244] [<ffffffffa058dc5e>] intel_fbdev_initial_config+0x18/0x28 [i915]
[ 2.376246] [<ffffffff81063f2d>] async_run_entry_fn+0x37/0xcd
[ 2.376248] [<ffffffff8105b77e>] process_one_work+0x2b1/0x59e
[ 2.376251] [<ffffffff8105c768>] worker_thread+0x24f/0x38a
[ 2.376253] [<ffffffff8105c519>] ? rescuer_thread+0x2cf/0x2cf
[ 2.376255] [<ffffffff81061b7c>] kthread+0xf8/0x100
[ 2.376257] [<ffffffff813bb9ef>] ? _raw_spin_unlock_irq+0x2c/0x4a
[ 2.376260] [<ffffffff813bc43f>] ret_from_fork+0x1f/0x40
[ 2.376262] [<ffffffff81061a84>] ? kthread_create_on_node+0x1d4/0x1d4
-ss
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